#include<algorithm>
using namespace std;
struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right) {}
    
};
class Solution {
public:
    int calculateDepth(TreeNode* root) {
        if (root == nullptr)return 0;
        int left = calculateDepth(root->left) + 1;
        int right = calculateDepth(root->right) + 1;
        return max(left, right);
    }
};